Controller Method file extensions? (.xml or .php)

[eluser]Fenix[/eluser]
Nope, it doesn't. The period is left as is. When I echo $content_type it gives me ".xml", assuming the method is "categories.xml", but if it is "categories.php" it won't even go to the controller because it thinks I am looking for an actual file named "categories.php".

I tried adding a custom route to routes.php like this:
$route['api/categories.php'] = 'api/categories';

It doesn't work but I didn't expect it to...

Any other ideas?